Method oe and apparatus for producing- and distributing electric



E. F. W. ALEXANDERSON.

METHOD OF ANDAPPARATUS FOR PRODUCING AND DISTRIBUTING ELECTRIC CURRENT WAVES 0F RADIOFREOUENCY.

APPLlCATION FILED AUG-5, 1915- 1,386,83 3 SHEET E Fig. I S-SHEET F/ Fig z.

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Patented Aug. 9, 1921.

E. F. W. ALEXANDERSON.

METHOD OF AND APPARATUS FOR PRODUCING AND DISTRIBUTING ELECTRIC CURRENT WAVES 0F RADIOFREQUENCY.

APPLICATION FILED AUG-5, I915.

1,886,830. Patented Aug. 9, 1921.

3 SHEETS'SHEET 2.

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I/VI/II HUI/W Inventor Ernst F. W. fI Iexanderson,

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E. F. W. ALEXANDERSON. METHOD OF AND APPARATUS FOR PRODUCING AND DISTRIBUTING ELECTRIC CURRENT WAVES 0F RADIOFREQUENCY. APPLICATION FILED Aue.5. 1915.

1,386,830. Patented'Ang- 9, 1921.

3 SHEETS-SHEET 3.

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Inventor- Ernst. FIW..' T lexander'sgn,

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UNITED STATES PATENT OFFICE.

ERNST F. W. ALEXANDER-SON, 0F SOHENEGTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATIGN OF NEW YORK.

METHOD OF AND APPARATUS FOR PRODUCING AND DISTRIBUTING ELECTRIC- CURRENT TTJAVES 0F RADIOFREQUENCY.

Application filed August 5, 1915.

To (ZZZ whom it may concern:

Be it known that I, ERNST F. W. ALEX- ANDERSON, a citizen of the United States, residing at Schenectady, in the county of Sichcnectady, State of New York, have in vented cer ain new and useful Improvements in Methods of and Apparatus for Producing and Distributing Electric-Current Waves of Radiofrequency, of which the following is a specification.

My invention relates to the production and distribution of alternating or pulsating electric impulses or electric current waves of radio frequency, and in particular to the production of an electric current wave of radio frequency which is the equivalent of two electric current waves of different frequencies and of substantially constant amplitudes. Broadly, the object of my inven tion is to provide a novel and improved method of and apparatus and system for producing and distributing electric current waves of radio frequency. More particu larly, the object of my invention is to provide a novel and improved method of and apparatus for producing an electric current wave which is the equivalent of, or, in other words, may be resolved into, two electric current waves of different frequencies and of substantially constant amplitudes. Other objects of my invention will appear in the course of the following description.

The use of electric current waves of two different radio frequencies appears to he often desirable in systems of radio communication. F or example, it has been proposed to send and receive signals with electric current waves of two different radio frequencies in order to secure greater selectivity, and again in order to reduce static disturbances. Where the use of two waves of different frequencies is desirable, a simple and convenient method of generating or producing such waves becomes important, and, in particular, it becomes desirable and important to provide a simple method of producing such waves, or their equivalent, from a single alternator of radio frequency. lviy present invention thus has for one of its objects the provision of a simple method of and apparatus for producing two electric current waves of different radio frequencies by producing a composite electric current wave which is the equivalent of the two de- Specification of Letters Patent.

Patented A11 9, 1921.

Serial No. 43,725.

sired waves and which may be resolved into the desired waves by selective tuning.

My present invention will best be understood by analyzing the combined wave which is produced by two electric current waves of different frequencies, and of the same amplitudes. The combined wave appears at first sight to be a simple wave of intermediate frequency with amplitude-pulsations, but it is found upon further analysis that every other group of amplitudepulsations is of opposite phase from the intermediate groups. That is to say, the individual impulses in every other group of Waves are opposite in phase to corresponding impulses in the intermediate groups of waves, or, in other words, corresponding impulses in any two adjacent groups of am plitude-pulsations are opposite in phase. The wave can be thought of as produced by a generator of the alternate-pole type, in which the exciting current is varied from a positive maximum to a negative maximum in accordance with the sine Wave law and with a frequency corresponding to the difference between the two frequencies into which the combined wave may be resolved in order to produce the Waves of the two desired frequencies. While this explanation may be used for describing the charactor of the combined wave, this particular method of producing the combined wave is not practical, since it is not feasible to'build altcrnators of the alternate-pole type of radio frequency.

The principal object of this invention is then to provide a practical method of and apparatus for producing electric current waves of radio frequency equivalent to those that would be produced by an alternate-pole machine with reversible excitation varied according to the sine wave law, thereby producing a composite electric current wave which can be resolved into two waves of constant amplitudes, the one of a higher and the other of a lower impulse frequency than the fundamental wave. The principal method. of my present invention consists in producing a fundamental electric current wave of constant amplitude and varying the amplitudes of the pulsations or impulses of thi fundamental wave to produce a composite electric current wave with amplitude pulsations, which can be resolved into two electric current waves of constant amplitudes, the one of a higher and the other of a lower impulse frequency than the fundamental wave. In carrying out this method, I employ a source of pulsating electric current of radio frequency and of constant amplitude in combination with means for modifying the amplitudes of the electric current wave in accordance with the sine wave law so that every other maximum of the ampl1- tilde-pulsations derives a current from the source of energy in an opposite direction to the intermediate maXima of the amplitudepulsations.

In another aspect, my present invention comprises a novel method of and apparatus for controlling the flow of power in an electric circuitof radio frequency by means of an electric current of a lower frequency, so that the resultant current flowing in the circuit is of such a character that it can be resolved into two currents of constant amplitudes with a difference in frequency equal to the frequency of the controlling current. In still another aspect my invention consists in controlling the flow of power from a source of radio frequency current of constant amplitude by means of a controlling current of lower frequency in such a way that a simple sine wave amplitude-pulsation is produced which can be resolved into three components, one of a higher frequency, one of a lower frequency, and one of the same frequency as the fundamental, and neutralizing the component of the same frequency as the fundamental by means of an electro motive force derived from the same source of power as the fundamental.

The novel features which I believe to be patentably characteristic of my invention are definitely indicated in the claims appended hereto. The novel method of my present invention and the arrangement and mode of operation of an apparatus and system for carrying out this method will be understood from the following description taken in connection with the accompanying drawings, in which:

F igures 1-7 inclusive are explanatory diagrams; and Figs. 8 and 9 diagrammatically represent two arrangements of apparatus in a system of radio communication for carrying out my invention.

Referring to Fig. 7 of the drawings, the waves B and C represent the two electric current waves of different frequencies and of constant amplitudes which it is desired to produce. Vhen combined the waves Band C produce the wave A. The wave A is thus a composite wave which may be resolved into the two waves B and C. It will be observed that the frequency of the pulsations or impulses of the wave A is intermediate the f equencies of the impulses of the waves B and C, and that the amplitudes of the pulsations of the wave A follow the sine law, so that the wave may be described as having amplitude-pulsations substantially in accordance with the sine wave law. It will furthermore be noted that each maximum pulsation of the wave A is opposite in phase to the two adjacent maximum pulsations. Thus, the maximum pulsation a is opposite in phase to the two adjacent maximum pulsations a. It thus follows that the pulsations or impulses in every other group of waves of the composite wave A are opposite in phase to corresponding impulses in the intermediate groups of waves, or, as heretofore stated, every other group of amplitude-pulsations is of opposite phase from the intermediate groups.

The preferred arrangement of apparatus for carrying out my invention is shown in Fig. 8. The source of pulsating electric current energy of radio frequency is represented as an alternator 10 feeding a transformer adapted for radio frequencies. The transformer has a secondary winding 11 with its middle point connected to one terminal of a local circuit, and in the system illustrated this terminal is shown as the ground. The other terminal of the local circuit is the antenna 14, and this terminal is connected through two magnetic controllers or amplifiers M and N to both of the outside terminals of the secondary winding 11. The primary winding of the trans former is composed of two sections 12 and 13 which are inductively related to the two sections of the secondary winding 11 resulting from the intermediate ground connection. The antenna is provided with the usual tuning inductance 15.

The magnetic controllers or amplifiers are in principle of that type described in my U. S. Patent 1206,6455. In my application for Letters Patent of the United States. Serial No. 623,438 filed November 26, 1915, I have described at length the construction and principle of operation of the particular form of magnetic controller which is diagrammatically represented in the accompanying drawings. Each magnetic controller comprises a t'wo'coil reactive winding 16 mounted upon independent magnetic cores and surrounded by a suitable control.- ling winding. The two coils of the reactive winding 16 of each magnetic controller are so arranged that their magnetizing actions are opposite. The windings 16 are included in the local t-ircuit in series relation with thcondary winding 11 of the radio trans former. Each of the magnetic controllers is provided with two controlling windings. The principal controlling windings 17 of the two magnetic controllers are fed from the same source of. current, which is shown in the drawings as an alternator 19 of lower frequency than that of the alternator 10.

The frequency of the alterator 19 controls the frequency of theamplitude pulsations of the composite electric current wave, as will be explained hereinafter. Each of the two magnetic controllers has another controlling winding 18, and both of these windings are supplied with direct current from any suitable source, shown in the drawings as a battery 20. The controlling windings 18 are so connected to the battery 20 that their magnetic effects upon the two magnetic controllers are opposite with respect to the instantaneous magnetic reactions of their respective controllers.

The relative values of the alternating and of the direct current controllingcircuits 17 and 18 are such that the maximum ampereturns of the alternating current circuit 17 is equal to the ampere-turns of the direct current circuit 18. This relation is represented in Fig. 1 of the drawings, where D represents the alternating controlling current derived from the alternator 19, and E represents the direct controlling current flowing in winding 18 of the magnetic controller M, while F represents the direct controlling current flowing in'the winding 18 of the magnetic controller N. The two windings 17 and 18 of the controller M are thus connected relatively in opposition to the two windings 17 and 18 of the controller N, so that the controller M has maximum controlling ampere-turns .when the controlling excitation of the controller N is zero. This will be clearly understood by referring to Figs. 2 and 3 of the drawings, in which the wave G represents the resultant controlling ampere turns of the controller M, while the wave H represents the resultant controlling ampere turns of the controller N. It will of course be understood that the'wave Gr is obtained by combining the wave D with the constant current E, Fig. 1, while the wave H is obtained by combining the wave D with the constant current F, Fig. 1. It will be observed from Figs. 2 and 3 that the maxima of the wave G occur at the minima of the wave H, and vice versa.

The characteristics of the magnetic controllers or amplifiers M and N are such that the impedance of each high frequency reactive winding 16 varies between practically open-circuit and short-circuit when the controlling excitation varies from zero to maximum, respectively. Thus, when the current wave of the controlling alternator 19 is a maximum, one of the magnetic controllers acts as a. short-circuit connecting the antenna to one terminal of the transformer, while the other amplifier interposes an impedance substantially equivalent to an opencircuit in the connection to the other terminal. After the phase of the controlling current wave supplied by the alternator 19 is changed 180 electrical degrees, the other amplifier acts as a short-circuit and the first as an open-circuit, thus reversing the polarity of the radio frequency current led to the antenna. At intermediate points, the voltage varies between these two extremes in accordance with the sine wave law. A. condenser 9.1 is shown in series with each of the magnetic controllers, and is to be considered a part of the same, since it is used to neutralize the leakage inductance in the windings thereof so as to bring the minimum value of the impedance as near as possible to a short-circuit.

It will be obvious from the foregoing description of the arrangement of apparatus for carrying out my invention that the flow of current to the antenna is so rontrolled that the effect is the same as if the polarity of the alternator was reversed during each half cycle of the controlling current. This will be better understood by referring to Figs. 4;, 5 and 6 of the drawings. The frequency of the alternating current generated by the alternator 10 is represented by the impulses in these figures. Fig. 4 represents the effect upon the amplitudes of the pulsationsof the radio frequency current supplied by the alternator 10 produced by the controlling excitation of the current wave Gr. Fig. 5 represents the effect produced upon the same high frequency pulsations by the controlling excitation of the current wave H. Fig. 6 represents the resultant of Figs. 1 and 5, and is the current wave supplied to the antenna. It will be observed that the current wave of Fig. (3 has an amplitude-pulsation substantially in accordance with the sine wave law and the impulses in every other group of waves are opposite in phase to corresponding impulses in the intermediate groups of waves. In fact, the wave of Fig. 6 is identical with the wave A of Fig. 7, and is hence the desired composite wave which can be resolved into the two waves and C of different frequencies. but of constant amplitudes.

The wave of Fig. 4 may be resolved into three components of substantially constant amplitude, one having a frequency equal to that of the fundamental, one of higher frequency, and one of lower frequency. The wave of Fig.5 also may be resolved into three components in the same way. The component of fundamental frequency af the wave of Fig. at, however, is equal and opposite in phase to the component of fundamental frequency of the wave of Fig. 5. Hence these two components neutralize each other and the resultant wave is made up entirely of a combination of the two components of higher and lower frequency than the fundamental.

The neutralization of the component of fundamental frequency is perhaps illustrated more clearly by the arrangement shown in Fig. 9. In this case a single magnetic amplifier l l is used in the one polarity, the

other polarity being connected to the an-.

case be connected in series as shown in the figure. The current through amplifier N will have a wave form such as is indicated in Figs. el and 5. The component of fundamental frequency of this wave which is of substantially constant amplitude is neutralized by an equal and opposite component of fundamental frequency which flows through inductance 25, hence the resultant wave which is supplied to the antenna will be made up entirely of the components having frequencies greater and less than the fundamental and will have the form indicated in Figs. 6 and 7.

The components having frequencies greater and less than the fundamental may be termed modulated components since these components are the only ones which are effective in signaling and the component of fundamental frequency may be termed the unmodulated component.

The apparatus which I have herein illustrated for carrying out my invention thus comprises generally an electric circuit including two parallel paths for the flow of electric current. These two paths are electrically associated at one end with opposite terminals of the source 10. That is to say, the path including the magnetic controller M, of Fig. 8, or the inductance 25 of Fig. 9, is electrically connected to one terminal of the alternator 10, while the path including the magnetic controller N, or the magnetic controller N, iselectrically connected to the other terminal of the alternator 10. The other ends of the two parallel paths are connected together and to the antenna 14.

The magnetic controllers M and N of Fig. 8 vary the impedance of each of the parallel paths in accordance with the sine wave law, and the controlling excitation of the two controllers is such that the impedance of the controller M is a maximum when the impedance of the controller N is a minimum, and vice versa. Thus, the effective path for the flow of current alternately shifts from one of the parallel paths to the other parallel path. In the apparatus of Fig. 9, the impedance of the magnetic controller N varies from a substantial short-circuit to substantially an open-circuit, in accordance with the sine-wave law, so that, just as in the apparatus of Fig. 8, the efiective path for the flow of current alternately shifts from one of the parallel paths to the other. The frequency of this change in the effective path for the flow of current is determined by and corresponds to the frequency of the controlling current derived from the alternator 19 or 19, as the case may be. The two terminals of the alternator 10 are, accordingly, alternately connected to the electric circuitincluding the antenna 14.

Throughout the specification and claims I have used the words impulse and pulsation to describe the individual pulsations or alternations of the electric current wave, while I have used the term amplitude-pulsation to describe the pulsation in the amplitudes of the individual impulses of the wave. Thus, in Figs. 4, 5, 6, and 7, the individual impulses or pulsations of the wave are represented by full lines, while the amplitude-pulsations are indicated by dotted lines.

hat I claim as new and desire to secure by Letters Patent of the United States, is:

1. The method of producing an electric current wave which is the equivalent of two electric current waves of different frequencies and of constant amplitudes, which consists in producing from a single source of energy a fundamental electric current wave of a frequency intermediate the frequencies of said two electric current waves, and varying the amplitudes of the pulsations of said fundamental electric current wave to produce an electric current wave with amplitude pulsations which can be resolved into three electric current waves of constant amplitudes one of the fundamental frequency, one of a higher and one of a lower frequency than said fundamental electric current wave and neutralizing the wave of fundamental frequency by means of an electromotive force derived from the same source of power.

2. The method of producing an electric current wave having amplitude pulsations substantially in accordance with the sine wave law in which the impulses in every other group of waves are opposite in phase to corresponding impulses in the intermediate groups of waves, which consists in producing a fundamental electric current wave of radio frequency, passing said wave through two impedances alternately varying from a maximum to a minimum, and combining the resultant effects of said two impedance upon said fundamental electric current wave to produce the desired electric current wave.

3. The method of producing an electric current wave of radio frequency with amplitude pulsations 0f sine wave character in which corresponding impulses of any two adjacent groups of amplitude pulsations are opposite in phase, which consist in deriving a fundamental electric current wave from a source of pulsating electric current energy of radio frequency and of substantially constant amplitude, subjecting said fundamental wave to the action of two impedances alternately varying from their respective maximum and minimum values at a frequency lower than that of the fundamental wave, and combining the waves resulting from the actions of said variable impedances to produce the desired electric current wave.

4;. The method of producing an electric current wave of radio frequency with amplitude pulsations of sine wave character in which corresponding impulses of any two adjacent groups of amplitude pulsations are opposite in phase, which consists in deriving a finidamental electric current wave from a source of pulsating electric current energy of radio frequency and of substantially constant amplitude, subjecting said fundamental wave to the action of two impedances, varying the values of said impedances substantially in accordance with the sine wave law and so that the maximum value of one impedance coincides with the minimum value of the other impedance, and combining the waves resulting from the actions of said variable impedances to produce the desired electric current wave.

5. An apparatus for producing an electric current wave having amplitude pulsations in. which the impulses of alternate amplitude pulsations are opposite in phase to corresponding impulses of intermediate amplitude pulsations comprising in combination a source of pulsating electric current energy of radio frequency and of substantially constant amplitude, an electric circuit associated with said source, an impedance in said circuit, and means for controlling the value of said impedance from a maximum to a minimum value and for alternately changing the effective path for the flow of cur rent in said circuit from one terminal of said source to the other terminal thereof at a frequency lower than that of said source.

6. A system of electrical distribution comprising in combination a source of pulsating electric current energy of radio frequency, an electric circuit associated with said source, a second source of pulsating electric current energy of lower frequency than said first mentioned source, and an electromagnetic means operatively related to said circuit and controlled by an electric current derived from said second source for alternately changing the effective path for the flow of current in said circuit from one terminal of said first mentioned source to the other terminal thereof.

7 A system of electrical distribution comprising in combination a source of pulsating electric current energy of radio frequency, an electric circuit including two parallel paths for the flow of current, said two parallel paths being electrically associated at one end with opposite terminals of said source and electrically connected together at the other end, and means associated with said parallel paths for alternately changing the effective path for the flow of current from one of said parallel paths to the other at a frequency lower than that of said source.

8. A system of electrical distribution comprising in combination a source of pulsating electric current energy of radio frequency, an electric circuit including two parallel paths for the flow of current, said two parallel paths being electrically associated at one end with opposite terminals of said source and electrically connected together at the other end, an impedance associated with each of said parallel paths, and means cooperating with said impcdances for alternately changing the effective path for the flow of current from one of said parallel paths to the other at a frequency lower than that of said source.

9. A system of electrical distribution comprising in combination a source of pulsating electric current energy of radio frequency, an electric circuit including two parallel paths for the flow of current, said two parallel paths being electrically associated at one end with opposite terminals of said source and electrically connected together at the other end, and means for varying the impedance of each of saic parallel paths substantially in accordance with the sine wave law and so that the impedance of one path is a maximum when the impedance of the other path is a minimum.

10. A system of electrical distribution comprising in combination a source of pulsating electric current ener y of radio frequency, an electric circuit including two parallel paths for tl flow of current, said parallel paths being electrically associated at one end wi h opposite terminals of said source and electrically connected together at the other end, a magnetic controller associated with each of said parallel paths, and means for varying the impedance of each of said magnetic controllers substantially in accordance with the sine wave law and so that the impedance of one controller is a maximum when the impedance of the other controller is a minimum.

11. A system of electrical distribution comprising in combination a source of pulsating electric current energy of radio frequency, an electric circuit including two parallel paths for the flow of current, said two parallel paths being electrically associated at one end with opposite terminals of said source and electrically connected together at the other end, and means including a pulsating magnetization means of a lower frequency than that of said source and a uni-directional magnetization means for varying the relative impedances of said two parallel paths so that the effective path for the flow of current alternately shifts from one of said parallel paths to the other.

12. A system of electrical distribution comprising in combination a source of pulsating electric current energy of radio frequency, an electric circuit including two parallel paths for the flow of current, sald two parallel paths being electrically associated at one end with opposite terminals of said source and electrically connected together at the other end, a reactive winding associated with each of said parallel paths, and means including a pulsating ma gnetization means of a lower frequency than that of said source and a uni-directional magnetization means for varying the relative impedances of said reactive windings so that the effective path for the flow of current alternately shifts from one of said parallel paths to the other.

13. A system of electrical distribution comprising in combination a source of pulsating electric current energy of radio fre quency, an electric circuit including two parallel paths for the flow of current, said parallel paths being electrically associated at one end with opposite terminals of said source and electrically connected together at the other end, a reactive winding associated with each of said parallel paths, a controlling winding operatively related to each of said reactive windings, a second source of pulsating electric current energy of a lower frequency than said first mentioned source electrically associated with said controlling winding, a second controlling winding operatively related to each of said re: ctive windings, and means for con necting said second controlling winding to a source of electric current energy so that the two controlling windings for each react. winding are respectively opposite in 141. The method of producing an electric current wave having amplitude pulsations in which the impulses of alternate amplitude pulsations are opposite in phase to corresponding impulses of intermediate amplitude pulsations, which consists in deriving from a single source of energy a fundamental electric current wave of radio frequency and producing amplitude pulsations in said wave in such a way that the resultant wave having amplitude pulsations may be resolved into three electric current waves of constant amplitude, one of the fundamental fremental electric current wave of radio frequcncy, producing amplitude pulsations in said wave in such a way that the resultant wave having amplitude pulsations is the equivalent of three electric current waves of constant amplitude, one of fundamental frequency, one of a higher and one of a lower frequency than said fundamental electric current wave and neutalizing the wave of fundamental frequency by a wave which is equal thereto and opposite in phase.

16. The method of controlling the flow of current in an electric circuit from a source of radio frequency energy which consists in producing by means of a controlling current of lower frequency, amplitude pulsations in the current in said circuit and periodically reversing with respect to the source and at a frequency corresponding to that of the controlling current the direction of current flow in the circuit.

17. in a radio signalin system the method of transmission which consists in producing a low frequency modulating wave, produc-v ing by means of said modulating wave a continuous radio frequency wave which is the equivalent of two electric current waves of frequencies which differ from each other by a value equal to twice the frequency of the modulating wave and transmitting said radio frequency wave to the exclusion of other radio frequency waves.

18. The method of controlling the flow of current in an electric circuit from a source of radio frequency energy which comprises two parallel paths connected at one end to opposite terminals of said source and connected together at the other end, which consists in varying the values of the impedanc-es of said paths in accordance with variations in a controlling current of lower frequency and in such a way that the maximum value of the impedance of one path corresponds with the minimum value of the impedance of the other path. I

19. The method of controlling the flow of current from a source of radio frequency energy in an electric circuit which comprises two parallel paths connected at one end to opposite terminals of said source and connected together at the other end which consists inalternately changing the effective path for the flow of'current from one of said parallel paths to the other at a frequency lower than that of said source. 1

20. A system of electrical distribution comprising in combination a source of radio frequency current, an electric circuit associated therewith, a source of controlling current of lower frequency than that of the first 7 mentioned source, and means for periodically comprising in combination a source of radio frequency current, an electric circuit associated therewith, a source of controlling current of lower frequency than the first mentioned source, and means for alternately changing by means of said controlling current the effective path for the flow of current in said circuit from one terminal of said source to the other terminal thereof at a frequency corresponding to the frequency of said controlling current.

22. fr system of electrical distribution comprising in combination a source of radio frequency current, an electric circuit associated therewith, a source of controlling current of lower frequency than the first mentioned source, means operatively related to said circuit for varying the amplitude of the impulses of the electric current flowing in the circuit in accordance with variations in the controlling current, and means for periodically reversing with respect to said source and at a frequency corresponding to that of the controlling current, the direction of current fiow in said circuit.

28. The combination in an apparatus of the class described of a source of radio frequency current, an electric circuit associated with said source, a source of controlling current of lower frequency than the first mentioned source, and electromagnetic means operatively related to said circuit and operable by means of said controlling current for changing the effective path for the flow of current in said circuit from one terminal of said first mentioned source to the other terminal thereof, and for varying the amplitude of the impulses of the current flowing in said circuit in accordance with variations in said controlling current.

24. The combination in an apparatus of the class described of a source of radio frequency current, an electric circuit associated with said source, a source of controlling current of lower frequency than the first mentioned source. and electromagnetic means operatively related to said circuit and operable by means of said controlling current for changing the effective path for the flow of current in said circuit from one terminal of said first mentioned source to the other terminal thereof at a frequency corresponding to that of the controlling current.

25. The combination in an apparatus of the class described, of a source of radio frequency current, an electric circuit associated therewith, a source of controlling current of lower frequency than the first mentioned source, an impedance in said circuit, and means for controlling the value of said impedance in accordance with variations in the controlling current and for alternately changing the effective path for the flow of current in said circuit from one terminal of said first mentioned source of the other terminal thereof at a frequency corresponding to the frequency of the controlling current.

26. A system of eleJtrica-l distribution comprising in combination a source of radio frequency current, an electric circuit including two parallel paths for the flow of current, said two parallel paths being electrically associated at one end with opposite terminals of said source and electrically connected together at the other end, a sourceof controlling current of lower frequency than the first mentioned source, and means associated with said parallel paths and operable by means of said controlling current for alternately changing the effective path for the flow of current from one of said parallel paths to the other.

27. A system of electrical distribution comprising in combination asource of radio frequency current, an electric circuit including two parallel paths for the flow of current, said two parallel paths being electrically associated at one end with opposite terminals of said source and electrically connected together at the other end, a source of controlling current of lower frequency than the first mentioned source, an impede ance associated with each of said parallel paths and means cooperating with said impedances and operable by means of said controlling current for alternately changing the effective path for the fiow of current from one of said parallel paths to the other at a frequency corresponding to that of the con trolling current.

28. A system of electrical distribution comprising in combination a source of radio frequency current, an electric circuit including two parallel paths for the flow of current, said two parallel paths being electrically associated at one end with opposite terminals of said source and electrically connected together at the other end, a source of controlling current of lower frequency than the first mentioned source, and means for varying the impedance of said parallel. paths in accordance with variations in said controlling current and in such a way that the impedance of one path is a maximum when the'impedance of the other path is a minimum.

29. A system of electrical distribution comprising in combination a source of radio frequency current, an electric circuitincluding two parallel paths for the flow of current, said two parallel paths being electrically associated at one end with opposite terminals of said source and electrically connected together at the other end, a source of controlling current of lower frequency than the first mentioned source, a magnetic controller associated with each of said parallel paths, and means for varying the impedance of each of said magnetic controllers in accordance with. variations in the controlling current and so that the impedance of one controller is a maximum when the impedance of the other controller is a minimum.

30. The method of operating an electrical distribution system which comprises two parallel paths which consists in producing radio frequency currents in each of said paths, the phase of the current in one of said paths being opposite to the phase of the current in the other path, and varying the mpedances of said paths in such a way that I the impedance of one is a maximum when the impedance of the other is a minimum.

31. The method of operating a radiating system which comprises two parallel paths for supplying energy thereto, which consists in producing radio frequency currents in each of said paths, the phase of the current in one of said paths being opposite to the phase of the current in the other path, varying the impedance of said paths in such a way that the impedance of one is a maximum when the impedance of the other is a minimum, and supplying energy from both of said paths to the radiating system.

32. In a radio signaling system, the method of transmitting electrical energy which consists in producing a low frequency modulating wave, producing a continuous radio frequency wave whose amplitude is directly proportional to said low frequency modulating wave, and transmitting said continuous radio frequency wave to the exclusion of other radio frequency waves.

33. In a radio signaling system, the method of transmission which consists in producing a low frequency modulating wave, producing a radio frequency continuous wave, modulating by means of the low frequency wave the amplitude of the radio frequency wave in such a. way that its amplitude is directly proportional to the low frequency wave, and transmitting the resultant radio frequency wave to the, exclusion of other radio frequency waves.

3%. In a radio signaling system, the combination of a source of low frequency modulating waves, a radio frequency alternating current generator adapted to generate sustained undamped oscillations, means for modulating the oscillations produced by said generator so that they will have an amplitude directly proportional to the low frequency modulating waves, and means for transmitting the resultant radio frequency wave to the exclusion of other radio frequency waves.

35. The method of preventing the radiation of the unmodulated component of a signaling wave which consists in superposing upon said wave an unmodulated wave of equal. value, but of phase opposite to that of the said uninodulated component.

36. The method of preventing the radiation of the unmodulated component of a signaling wave which consists in opposing said component by an equal wave.

7 In witness whereof, I have hereunto set my hand this 4th day of August, 1915.

ERNST F. W. ALEXANDERSON. 

